Unfinished series piss me off

I love reading fiction. That said, unfinished series piss me off. I try to find ones that are complete so I don't go bananas waiting for the next book in the series. Yet this has happened again. I have been tricked into reading a series that seemed complete but was not. WTF. At least authors should bother to say that there's yet another book planned so I don't make the tragic mistake of starting the stupid series in the first place. But no, they have to drive us all insane. Urgh.